Exposure of NK cells to monokines IL-12 and IL-18 results in substantial AICL cell surface expression and NKp80 downregulation. NK cells purified from freshly isolated PBMC were cultivated in presence of IL-12 and IL-18 as well as IL-2. (A) Surface expression of AICL and NKp80 by NK cells cultivated for the indicated times. Flow cytometric analyses of cells stained with mAb 7F12 (anti-AICL, upper) or 5D12 (anti-NKp80, lower) (open histograms) or isotype controls (gray). One representative experiment out of 4 is shown. (B) Kinetics of AICL or NKp80 transcript levels of monokine-stimulated NK cells with levels of untreated NK cells arbitrarily set as 1. Means of triplicates are shown with standard deviations. Experiments with NK cells from 3 different donors gave similar results. (C) Total AICL glycoproteins in lysates of purified NK cells or NK cell–depleted PBMC cultivated for 2 days without additives (ø) or in the presence of IL-12 and IL-18 (IL) or PMA. AICL was detected with mAb 7G4 in immunoblotting, and actin used as loading control.